Crankcase Ventilation System

ABSTRACT

A system for venting crankcase emissions from an engine is disclosed generally comprising a crankcase emissions conduit that communicates blow-by gases from the crankcase into the exhaust flow of an exhaust conduit, which includes a venturi, via an inlet located upstream of the minimum inner diameter of the venturi in order to pump the crankcase emissions therethrough. In certain embodiments, the gases are then directed to a filter assembly, which may include a particulate filter and may include a catalyst for facilitating redox of harmful substances to create harmless compounds prior to venting them or recirculating them in the system. In certain advantageous embodiments, an auxiliary oxygen supply is provided to facilitate these burning processes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/249,286, filed Oct. 13, 2005, which application is currently pendingand which application is hereby incorporated by reference herein in itsentirety.

FIELD OF THE INVENTION

The present invention relates to a system for venting crankcaseemissions from an engine. More specifically, the invention relates to asystem for routing the crankcase emissions to the exhaust system of avehicle for subsequent filtering.

BACKGROUND OF THE INVENTION

As is well know, all piston engines produce some crankcase gases thatmust be emitted from the crankcase. These crankcase emissions, sometimesreferred to as “blow-by” gases, are the result of exhaust gases thatleak down into the crankcase from the combustion chamber of the engine'spiston cylinders via gaps between the cylinder walls and the pistonrings due to the high pressures in the cylinders during compression andcombustion. Moreover, the volume of these gases increases over time, asthe cylinder liners and piston rings wear, thereby producing moreexhaust gas leakage from the combustion chambers.

Because of this leakage, the pressure in the crankcase will rise.However, this pressure should ideally be maintained at a level equal to,or slightly less than, atmospheric pressure in order to avoid causingexternal oil leakage through various gasketed joints. Therefore, inorder to prevent the crankcase gases from pressurizing the crankcase,they must be continually vented therefrom.

Though these gases could be vented to the atmosphere, environmentalawareness of crankcase emissions has increased significantly in recentyears. As engine emissions have been reduced, the crankcase emissions,which contribute to air pollution, have increasingly become a moresignificant portion of total engine emissions. Recent regulations haveeliminated exceptions for crankcase emissions, treating them the same asother exhaust emissions. Therefore, while it is possible to filter andvent the crankcase emissions to the atmosphere, this method can only beemployed when the emission requirements can be satisfied for both theexhaust and crankcase emissions combined.

An alternative to venting these gases to the atmosphere is routing themto the air intake, such as, for example, the systems disclosed in U.S.Pat. No. 6,261,333 to Dickson and U.S. Pat. No. 6,575,022 to Schneideret al. However, as these gases pass through the crankcase, they becomecontaminated with oil mist. If a crankcase vent is connected directly tothe air induction system, the dirty, oily mist may have various illeffects on the engine. This is particularly true in turbochargedengines, where the undesirable consequences of unfiltered crankcaseemissions introduced into the engine's air intake can include a decreasein the efficiency of the turbocharger due to coke deposits on theturbine, or a reduction in the performance of the intercooler due to theaccumulation of oil, and a significant shortening of the life of theengine. Therefore, it is necessary to filter the crankcase gases priorto introducing them into the air induction system of the engine in orderto remove oil and soot, thereby requiring the use of additionalfiltering assemblies, such as an oil mist separator.

Another alternative, therefore, is to route the crankcase emissions tothe exhaust system, which typically already includes a mechanism fordisposing of undesirable substances in engine emissions. For example, ina diesel powered vehicle, a diesel particulate filter (DPF) may bepositioned in the flow path of the exhaust in order to reduce the amountof soot and harmful gases ultimately emitted. A DPF generally comprisesa ceramic filter that traps the particulates in the exhaust gas as itflows through the filter. At high exhaust temperatures, these trappedparticulates are burned, resulting in harmless carbon dioxide emissions.Typically, the DPF will employ catalysts—via either a separate catalystsection preceding the filter section or a catalyzed wall filtersection—to facilitate oxidation, thereby converting harmfulcompounds—like hydrocarbons and carbon monoxide—into harmless compounds.Similarly, the use of a catalyst can facilitate oxidation of the carbonstrapped in the particulate filter to burn these particulates at lowertemperatures. However, the use of such a system may require additionalenergy consumption to pump the crankcase emissions into the exhaustflow.

What is desired, therefore, is a system for venting blow-by gases fromthe crankcase of an engine. What is further desired is system ofcrankcase ventilation that does not require additional filteringassemblies to burn harmful compounds in these emissions. What is alsodesired is a system that does not require excessive energy consumptionto vent and filter the gases.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide asystem for the ventilation of blow-by gases from the crankcase of anengine that results in the emission of harmless compounds.

It is a further object of the present invention to provide a system forventing a crankcase that permits the usage of filtering mechanisms thatare already present in the vehicle.

It is yet another object of the present invention to provide a systemfor venting a crankcase that is powered by energy already available inthe system.

In order to overcome the deficiencies of the prior art and to achieve atleast some of the objects and advantages listed, the invention comprisesa crankcase ventilation system, including an exhaust gas conduit throughwhich exhaust gas flows from an engine, and a crankcase emissionsconduit through which crankcase emissions flow from the engine, whereinthe exhaust gas conduit includes a crankcase emissions inlet throughwhich the crankcase emissions flow from the crankcase emissions conduitinto the exhaust gas conduit, and wherein the exhaust gas conduitincludes a reduced portion having a minimum inner diameter, the minimuminner diameter being located downstream of the crankcase emissionsinlet, for drawing the crankcase emissions therethrough.

In another embodiment, the invention comprises a crankcase ventilationsystem, including an exhaust gas conduit through which exhaust gas flowsfrom an engine, the conduit having an upstream portion and a downstreamportion, the upstream portion having an inlet, and a crankcase emissionsconduit through which crankcase emissions flow from the engine to theinlet and into the upstream portion of the exhaust gas conduit, whereinthe exhaust gas conduit includes a venturi portion located downstream ofthe upstream portion by which the pressure of the exhaust gas flowingtherethrough is decreased in order to pump the crankcase emissions intothe exhaust gas conduit and towards the downstream portion.

In yet another embodiment, the invention comprises a crankcaseventilation system, including an engine having a cylinder and acrankcase, the engine having an exhaust port through which exhaust gasis discharged from the cylinder, and a crankcase vent through whichblow-by gas in the crankcase is vented therefrom, an exhaust gas conduitin fluid communication with the exhaust port for communicating theexhaust gas therefrom, the conduit having a blow-by gas inlet and areduced portion having a minimum inner diameter located downstream ofthe blow-by gas inlet, a blow-by gas conduit in fluid communication withthe crankcase vent and the blow-by gas inlet, through which conduit theblow-by gas is communicated from the crankcase into the exhaust gasconduit upstream of the minimum inner diameter of the reduced portion ofthe exhaust gas conduit, and a filter assembly in fluid communicationwith the reduced portion of the exhaust gas conduit for receiving theexhaust and blow-by gases therefrom and burning particulates in thegases.

In still another embodiment, the invention comprises a method forventilating a crankcase, including providing an exhaust conduit with areduced portion having a minimum inner diameter, providing a filterassembly in fluid communication with, and downstream of, the reducedportion of the exhaust conduit, communicating exhaust gas from an enginethrough the exhaust conduit to the filter assembly, and communicatingcrankcase emissions from the engine into the exhaust conduit upstream ofthe minimum inner diameter of the reduced portion of the exhaust conduitsuch that the flow of exhaust gas pumps the crankcase emissions throughthe exhaust conduit to the filter assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a crankcase ventilation system inaccordance with the invention.

FIG. 2 is a side view in partial cross-section showing additional detailof the engine of the crankcase ventilation system of FIG. 1.

FIG. 3 is a side view in partial cross-section showing additional detailof the exhaust gas conduit of the crankcase ventilation system of FIG.1.

FIG. 4 is a side view showing additional detail of the filter assemblyof the crankcase ventilation system of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The basic components of one embodiment of a crankcase ventilation system10 in accordance with the invention are illustrated in FIG. 1. As usedin the description, the terms “top,” “bottom,” “above,” “below,” “over,”“under,” “above,” “beneath,” “on top,” “underneath,” “up,” “down,”“upper,” “lower,” “front,” “rear,” “back,” “forward” and “backward”refer to the objects referenced when in the orientation illustrated inthe drawings, which orientation is not necessary for achieving theobjects of the invention.

The system 10 includes an air inlet conduit 20 that supplies inlet airto an engine 22. As the inlet air flows through the conduit 20, it flowsthrough turbochargers 24, which compress the air, and is subsequentlyintroduced into the cylinders 26 of the engine 22 via an intake manifold28 (indicated by arrows A). After combustion, the exhaust gases aredischarged from the cylinders 26 and are directed to an exhaust gasconduit 30 via an exhaust manifold 32 (indicated by arrows B).

Referring to FIG. 2, each of the cylinders 26 includes a piston 34 towhich the crankshaft 42 is connected. By controlling the intake andexhaust valves 36, 38 and the fuel injector 40, the engine 22 generatescompression and combustion strokes via the compression and expansion ofgases in the cylinder 26 to cause the piston 34 to drive the crankshaft42. During this process, some of the gases leak down past the pistonrings 44 and into the crankcase 46 (indicated by arrows C). As a result,during the exhaust stroke, when the exhaust valve 38 is opened and thepiston moves in an upward direction to expel the exhaust gases from thecylinder 26, not all of the gases are discharged via the exhaust port48. Accordingly, in order to prevent excessive build-up of these gasesin the crankcase 46, and the undesired pressurization caused thereby, acrankcase vent 50 is provided, through which the crankcase (“blow-by”)gases are vented therefrom (indicated by arrows D).

Referring again to FIG. 1, after the exhaust gases are discharged fromthe cylinder 26, the exhaust gases flow through the exhaust conduit 30(arrows B). The exhaust gas flows through the turbochargers 24, spinningturbines 60, which, in turn, spin air pumps 62, thereby compressing theinlet air flowing through inlet air conduit 20 to increase power in theengine 22. The exhaust gas continues through the exhaust gas conduit 30to a venturi 64.

After the blow-by gases are vented from the crankcase 46, thesecrankcase emissions flow through a crankcase emissions conduit 70.toward the venturi 64. In certain embodiments, a filter 72 is positionedin the flow path of these crankcase emissions to provide some filteringof these gases prior to introduction into the venturi 64.

As shown in FIG. 3, the exhaust conduit includes an upstream portion 80and a downstream portion 82, and a venturi portion 84 downstream of theupstream portion 80. This venturi portion 84 includes a reduced portionof the inner wall 86. A crankcase emissions inlet 88 passes through thewall of the exhaust gas conduit 30, through which the crankcaseemissions are introduced from the crankcase emissions conduit 70 intothe exhaust conduit 30 (arrows D). The reduced portion of the inner wall86 has a minimum inner diameter located downstream of the inlet 88.Accordingly, the velocity of the exhaust gas is increased in thisregion, while the pressure decreases, thereby creating a low pressurearea directly adjacent the minimum inner diameter of the wall 86 thatserves as a sort of vacuum, which effectively pumps the crankcaseemissions into and through the venturi 84.

In certain advantageous embodiments, a sleeve 90, through which theexhaust gas flows, has an inlet end 92 and an outlet end 94, and atleast the outlet end 94 is positioned within the conduit wall 86.Accordingly, exhaust gas enters the sleeve 90 via inlet end 92, flowsthrough the sleeve 90, and exits the sleeve 90 via outlet end 94 (arrowsB). The sleeve 90 can be positioned such that the outlet end 94 at leastpartially occludes the inlet 88, thereby decreasing the flow ofcrankcase emissions into the exhaust gas conduit 30. At least a portionof the sleeve 90 can be displaced longitudinally along the exhaustconduit 30 to alter the extent to which the outlet end 94 occludes theinlet 88, allowing the introduction of blow-by gases into the exhaustgas conduit 30 to be regulated.

In certain advantageous embodiments, a portion of the sleeve 90 has athreaded outer surface 96, and a portion of the conduit wall 86 has acorresponding, threaded inner surface 98 for engaging the threadedsleeve surface 96. As a result, the outlet end 94 can be displaced alongthe exhaust conduit 30 by simply rotating the sleeve 90. In this way,the flow of crankcase emissions into the conduit 30 can be accuratelyand precisely controlled. In certain advantageous embodiments, thesleeve 90 and the conduit 30 are coaxial.

Various drive mechanisms may be employed to drive the sleeve 90 back andforth through the exhaust gas conduit 30, such as, in the case of athreaded sleeve, a drive mechanism designed to cause rotational movementof the sleeve 90, such as, for example, a gear (not shown) for engaginga corresponding surface on the sleeve 90, or, in the case of anunthreaded sleeve 90, a drive mechanism designed to cause linearmovement of the sleeve 90, such as, for example, a pinion (not shown)for engaging teeth on the underside of the sleeve 90.

In certain advantageous embodiments, the cross-sectional area of theoutlet end 94 is smaller than the cross-sectional area of the inlet end92, such that some throttling of the inlet air flowing through thesleeve 90 occurs in this reduced portion. In certain embodiments, thisreduced portion is simply a necked portion of the sleeve 90, and in someembodiments, it comprises a tapered section 100, which, for example, mayhave a frustoconical shape. Likewise, the cross-sectional area of aportion of the conduit 30 in which the outer end 94 of the sleeve 90moves is also reduced, providing a similar throttling effect. In someembodiments, this reduced section is necked or tapered, resulting in theventuri 84.

When the sleeve 90 is rotated longitudinally in the direction of theventuri 84, the annular, tapered section 100 of the sleeve 90 approachesthe annular, tapered wall of the venturi 84. In this way, the sleeve 90,in conjunction with the venturi 84, acts as a flow regulator for thecrankcase emissions entering the conduit 30 and mixing with the exhaustgas. The tapered section 100 of the sleeve 90 is designed with across-sectional area that decreases towards the tip of the outlet end94. Similarly, the venturi 84 has a cross-sectional area that decreasesin the direction of flow of the conduit 30. Furthermore, this reductionin the cross-sectional area of the venturi 84 is greater than thereduction in the cross-sectional area of the outlet end 94. Because ofthis arrangement, as the sleeve 90 is rotated in the direction of theflow through the conduit 30, the inlet 88 becomes smaller, restrictingthe amount of blow-by gases that are communicated into the exhaust gasconduit 30.

Moreover, as the size of the inlet 88 changes in accordance with themovement of the outlet end 94 of the sleeve 90, the point of entry ofthe crankcase emission into the flow of exhaust gas likewise changes.Accordingly, the greatest throttling of the exhaust gas flowing throughthe exhaust conduit 30 (i.e., passing through the outlet end 94 of thesleeve 90) is always achieved at the point at which the crankcaseemissions enter the conduit 30, independently of the position of thesleeve 90.

In some embodiments, a streamlined body 110 is disposed in the conduit30 that may be positioned to at least partly occlude the outlet end 94of the sleeve 90. Accordingly, in addition to the reduction resultingfrom the tapered section 100, further throttling of the exhaust gasflowing through the conduit 30 can be achieved by limiting the amount ofgas exiting the sleeve 90 by employing the streamlined body 110. Incertain advantageous embodiments, the streamlined body 110 has a taperedend 112, which may, for example, be ovoid in shape. Due to this shape ofthe tapered end 112, the space between the perimeter of the outlet end94 and the body 110 may be decreased and increased by moving the sleeve90 forward and backward along the conduit 30.

In some of these embodiments, the streamlined body 110 is fixed to theconduit 30 such that it remains stationary with respect to the conduit30. Accordingly, the flow of exhaust gas through the conduit 30 can becontrolled by moving the sleeve 90 back and forth over the end of thebody 110 to partly occlude, and vary the extent of occlusion of, theoutlet end 94 of the sleeve 90. In this way, the flow of exhaust gasthrough the conduit 30 can be rapidly increased with minimal movement ofthe sleeve 90 due to the sharp curve of the body 110.

In other embodiments, an actuator 114 is provided for displacing thestreamlined body 110 backwards and forwards along the conduit 30,causing the tapered end 112 to move back and forth through the outletend 94. In this way, the flow of exhaust gas through the conduit 30 canbe altered independently of the alteration of the blow-by gas flow. Theactuator 114 may be located outside of the conduit 30 and connected tothe body 110, or may located within the streamlined body 110 itself, asis described in published U.S. Patent Application No. US 2004/0099257 toBerggren et al., the specification of which is hereby incorporatedherein by reference.

With this arrangement, in addition to generally providing desirablemixing and pumping effects, the sleeve 90 can be used to control thespeed of the blow-by gas, while the body 110 can be used to control thespeed of the exhaust gas, and the relative speed between the two can becontrolled by coordinating the movement of the two. Furthermore, incertain embodiments, the sleeve 90 may be advanced far enough along theconduit 30 such that the flow of blow-by gas into the conduit 30 iscompletely shut off. The outlet end 94 can be advanced through thenecking of the venturi 84 until it comes flush up against the wall ofthe conduit 30, just downstream of the maximum diameter of the body 110.

In some embodiments, the streamlined body 110 is disposed in the conduit30 such that the maximum diameter of the body 110 is located downstreamof the sleeve 90, and the body 110 is positioned substantially outsideof the sleeve 90, as shown in FIG. 3. Accordingly, in these embodiments,the flow path is convergent until the point where the crankcaseemissions are introduced into the flow of the exhaust gas, and thus,does not become divergent until the two gases have mixed. However, inother embodiments, the streamlined body 110 may be located within thesleeve 90.

In other embodiments, no sleeve 90 may be used, and the streamlined body110 itself may be employed to vary the cross-sectional area of theconduit 30 through which both the exhaust gas and crankcase emissionsmay flow to the downstream portion 82 of the conduit, as is describedfor regulating the flows of both inlet air and recirculation exhaust gasin published U.S. Patent Application No. US 2004/0099257.

Referring again to FIG. 1, after flowing through the venturi portion 84,the exhaust and blow-by gases flow through the downstream portion 82 toa filter assembly 120 (indicated by arrows E), where they are filteredprior to venting them to atmosphere or returning them to the inletconduit 20 for recirculation through the system. The filter assembly 120may, for example, comprise a diesel particulate filter, such as anupstream diesel particulate filter or a wall-flow diesel particulatefilter, which includes an oxidation and/or reduction catalyst and aparticulate filter.

For example, referring to FIG. 4, in certain advantageous embodiments,the filter includes an inlet section 122, a catalyst section 124, afilter section 126, and an outlet section 128. The filter section 126comprises a particulate filter, which traps undesired particulates thatare present in the gases. The catalyst section 124 may include, forexample, a ceramic honeycomb coated with a redox catalyst, such asplatinum, palladium, or rhodium, to convert harmful compounds—namely,hydrocarbons, carbon monoxide, and nitrous oxides—into harmlesscompounds—namely, carbon dioxide and water, carbon dioxide, andnitrogen, respectively. The high temperature gases flow into the filtersection 126, and the particulates trapped therein are burned off. Asexplained above, a catalyst is typically employed to facilitateoxidation of the carbon particles to cause burning at lower exhausttemperatures. In certain embodiments, an auxiliary oxygen supply 130,such as a conduit for regular inlet air or a reserve of oxygen that iscontrollable by a valve 132, provides additional oxygen to the conduit30 in order to facilitate the burning process (indicated by arrow G).Though separate catalyst and filter sections 124, 126 have beendescribed herein, in some embodiments, instead of employing a honeycombor bead catalyst section upstream of the filter section 126, thecatalyst is integrated into the wall of the filter.

As noted above, after the gases have been filtered in this way, they maybe returned to the inlet conduit via a recirculation conduit 140 to berecirculated through the system, or may be safely vented to theatmosphere via a vent 142 (indicated by arrow F).

It should be understood that the foregoing is illustrative and notlimiting, and that obvious modifications may be made by those skilled inthe art without departing from the spirit of the invention. Accordingly,reference should be made primarily to the accompanying claims, ratherthan the foregoing specification, to determine the scope of theinvention.

1. A crankcase ventilation system, comprising: an exhaust gas conduit through which exhaust gas flows from an engine; and a crankcase emissions conduit through which crankcase emissions flow from the engine; wherein said exhaust gas conduit includes a crankcase emissions inlet through which the crankcase emissions flow from said crankcase emissions conduit into said exhaust gas conduit; and wherein said exhaust gas conduit includes a reduced portion having a minimum inner diameter, the minimum inner diameter being located downstream of said crankcase emissions inlet, for drawing the crankcase emissions therethrough.
 2. The system of claim 1, further comprising a filter assembly located downstream of the reduced portion of said exhaust gas conduit.
 3. The system of claim 2, wherein said filter assembly includes a particulate filter.
 4. The system of claim 3, wherein said filter assembly includes an oxidation catalyst.
 5. The system of claim 4, wherein said filter assembly comprises an upstream catalyst diesel particulate filter.
 6. The system of claim 4, wherein said filter assembly comprises a wall-flow catalyst diesel particulate filter.
 7. The system of claim 1, wherein said crankcase emissions conduit includes a filter.
 8. The system of claim 2, further comprising an auxiliary oxygen conduit through which oxygen flows, wherein said exhaust gas conduit has an auxiliary oxygen inlet through which the oxygen flows from said auxiliary oxygen conduit into said exhaust gas conduit.
 9. The system of claim 8, further comprising a control valve for regulating the flow of oxygen through said auxiliary oxygen inlet.
 10. The system of claim 2, further comprising an air inlet conduit through which inlet air is supplied to the engine; and a recirculation conduit through which gases flow from said filter assembly to said air inlet conduit.
 11. The system of claim 2, further comprising a vent through which gas flowing from said filter assembly is vented to the atmosphere.
 12. The system of claim 1, wherein the reduced portion of said exhaust gas conduit comprises a tapered venturi.
 13. The system of claim 1, further comprising: a sleeve disposed in said exhaust gas conduit and through which exhaust gas flows, said sleeve having an outlet end positionable along said exhaust gas conduit to at least partly occlude said crankcase emissions inlet and movable along a portion of said exhaust gas conduit to vary the extent of occlusion of said crankcase emissions inlet in order to regulate the flow of crankcase emissions into said exhaust gas conduit; and a streamlined body disposed in said exhaust gas conduit and positionable along said exhaust gas conduit to at least partly occlude the outlet end of said sleeve.
 14. The system of claim 13, further comprising an actuator for moving said streamlined body along said exhaust gas conduit to vary the extent of occlusion of the outlet end of said sleeve in order to regulate flow of exhaust gas out of said sleeve.
 15. A crankcase ventilation system, comprising: an exhaust gas conduit through which exhaust gas flows from an engine, said conduit having an upstream portion and a downstream portion, said upstream portion having an inlet; and a crankcase emissions conduit through which crankcase emissions flow from the engine to said inlet and into said upstream portion of said exhaust gas conduit; wherein said exhaust gas conduit includes a venturi portion located downstream of said upstream portion by which the pressure of the exhaust gas flowing therethrough is decreased in order to pump the crankcase emissions into said exhaust gas conduit and towards said downstream portion.
 16. The system of claim 15, further comprising a filter assembly in fluid communication with said venturi portion and downstream thereof for burning the crankcase emissions pumped through said venturi portion.
 17. The system of claim 16, wherein said filter assembly comprises an oxidation catalyst and a particulate filter for trapping and burning particulates.
 18. A crankcase ventilation system, comprising: an engine having a cylinder and a crankcase, said engine having an exhaust port through which exhaust gas is discharged from said cylinder, and a crankcase vent through which blow-by gas in said crankcase is vented therefrom; an exhaust gas conduit in fluid communication with said exhaust port for communicating the exhaust gas therefrom, said conduit having a blow-by gas inlet and a reduced portion having a minimum inner diameter located downstream of the blow-by gas inlet; a blow-by gas conduit in fluid communication with said crankcase vent and said blow-by gas inlet, through which conduit the blow-by gas is communicated from said crankcase into said exhaust gas conduit upstream of the minimum inner diameter of the reduced portion of said exhaust gas conduit; and a filter assembly in fluid communication with the reduced portion of said exhaust gas conduit for receiving the exhaust and blow-by gases therefrom and burning particulates in the gases.
 19. The system of claim 18, wherein said filter assembly comprises an oxidation catalyst and a particulate filter for trapping and burning the particulates.
 20. A method for ventilating a crankcase, the method comprising: providing an exhaust conduit with a reduced portion having a minimum inner diameter; providing a filter assembly in fluid communication with, and downstream of, the reduced portion of the exhaust conduit; communicating exhaust gas from an engine through the exhaust conduit to the filter assembly; and communicating crankcase emissions from the engine into the exhaust conduit upstream of the minimum inner diameter of the reduced portion of the exhaust conduit such that the flow of exhaust gas pumps the crankcase emissions through the exhaust conduit to the filter assembly.
 21. The method of claim 20, wherein the filter assembly comprises an oxidation catalyst and a particulate filter for trapping and burning particulates.
 22. The method of claim 20, further comprising the step of regulating the amount of crankcase emissions communicated into the exhaust conduit.
 23. The method of claim 20, further comprising the step of supplying an auxiliary flow of oxygen to the exhaust conduit.
 24. The method of claim 20, further comprising the step of filtering the crankcase emissions before communicating the crankcase emissions into the exhaust conduit. 